It's Advent of Code time again. After completing all of last years' in Haskell I've been unsure which language to use this time. I considered doing it in a language I barely know, to try to learn more, but I feel Advent of Code is about pure computation technique - how you think about a problem more than how you implement it. In my day job we took a decision recently to write new code in Kotlin so I'm going to do AoC this year in Kotlin, without an IDE so I'm really forced to learn the language and libraries rather than hunting and picking from autocomplete suggestions and relying on Gradle magic. I'm using syntax highlighting only and the command-line compiler with a Makefile.